Friday, March 3, 2017

Winter
is the time for charcoal making. At the bottom of Ikebuchi Open Space, where
Lovers of Niiharu meet at 9:00 every weekend, there is a hut. It looks like a
garage with 2 mini-pickups of the Lovers parked regularly. The structure is
actually a charcoal hut for 2 kilns. The idea of Niiharu Citizen Forest is to
recreate traditional husbandry of forests in Yokohama. Charcoal cooking was one
of the important jobs before the domination of fossil fuels. 20 or so years
ago, the current chairman of the Lovers, Mr. Okawa, attended classes organized
by the City, and transferred the knowledge, including a blueprint for kiln, of
charcoal making to the other members. Since then, several members of Lovers are
cooking charcoal in the facility every winter. The kilns have already accumulated
the tradition of the Lovers.

Here
it is.

There
are many designs for modern charcoal kilns in Japan. (Photos can be seen here.)
Niiharu’s kilns are different from that of Araizawa, or of Nature Sanctuary.
Basically, it is made of a drum of 57cm of diameter and 90cm tall, buried in
red clay. As this is for weekend forest volunteers, it’s not for cooking wood
charcoal for days, but for one day making with bamboos. Even though, I am
impressed with its clever low-tech, and sustainable for volunteers, structure.
The bottom of a drum has a hole of 11cm diameter. The bottom wall of the drum also
has 4 holes each of which has a welded pipe of 5cm diameter. The top of a drum
is a lid with a hole for a Ø3cm pipe. The drum is then put on a U shaped
concrete gutter as its Ø11cm hole is over the trough. The drum and gutter are held
by red-clay loaded in a space surrounded by 4 150cm*120cm metal walls. The clay
holds the drum and 4 pipes by piling up the square tightly to the rim of the
drum. So, when we see the kiln from a side, it looks like a metal box situated
on a clay mount with 4 pipes sticking out from the top.

Seeing
a Niiharu charcoal kiln from the side

A
sectional view of Niiharu’s charcoal kiln

It’s a
view from the above of the kiln.

The science
of charcoal making is, when we add heat on logs slowly but continuously in an almost
sealed-up space, they start to heat up themselves and release volatile
substances their cells hold. If we keep burning them by firewood, they will
eventually become ashes which are the materials, such as metals, that cannot
evaporate with the energy created by camp fires. In contrast, if we stop adding
external energy, but create tightly sealed environment for the heated logs,
they continue to burn themselves slowly with very limited supply of oxygen and discharge
instable oils from their body as much as possible. Though, without new fire supplied,
the closed structure eventually cools down and the self-combustion of logs
inside also stops. The logs burned in this way end up as a chunk of carbon.
They are now charcoals which are incompletely combusted logs in a shut room.
When a charcoal is very close to pure carbon, they do not contain volatile element
much. Unlike firewood, they can burn for a long time without creating flame.
That’s why before Japanese valued good quality charcoal as energy source. In
other words, a charcoal kiln intends to let the logs free the unstable elements
completely during combustion. Niiharu’s kilns are designed to do that just by
burning firewood in the concrete gutter.

The
difference between completely burned woods and charcoal.One of my senior
Lovers showed me how different they were.Completely burned woods looked like a
charcoal,but they were very fragile and easily became ashesjust by rubbing
them between the fingers.In contrast, our bamboo charcoal maintained its formand emitted metallic sound when we gently tapped them.

To
prepare charcoal cooking, the Lovers install a stovepipe that fits snuggly to
the hole at the bottom of the drum. We then fill the drum tightly with sticks
of bamboos. They are not just any trees from bamboo forests. We have to burn
them for quite a long time, if not for days. So, if a bamboo is too thin, it
would easily turn into ashes. We deliberately choose a large tree with thick
enough wall. Moreover, a wet log is not for efficient combustion. We start to
harvest bamboo logs in autumn before actual charcoal cooking begins and let
them dry in a shed for at least one month. This requirement effectively
excludes first-year trees for harvest since they contain lots of moisture. We cut
the harvested logs in 53cm, i.e. the same length of the pipe at the center. It
is possible to make a bamboo charcoal with the logs cut in this way which is called
Hanazumi花炭, or we split the logs
to create sticks. As inside of bamboos are chambers void of tree meat, charcoal
making with bamboo logs takes fewer hours, but the volume of product from one
operation is smaller. We also have to be careful for burning firewood as bamboo-log
will easily turn into ashes. We can stuff the drum with a larger volume of
bamboos in the form of sticks, but it takes more time to make charcoal. Niiharu
Lovers normally cook bamboo charcoal sticks, and make log charcoals when there
is a special order.

Inside
of a drum.The center is a hole for stovepipe.The wall of the drum has 4 holes
where pipes are welded to.

Removable
stovepipes

It
fits to the hole like this.

Drying
bamboos.Not all of them are for charcoals.We choose suitably-sized logs for
preparation.

Cutting
the logs to the size

We
then split the logs to make sticks.Bamboos are funny.They can be cracked
easilywhen we strike vertically with a machete.I learned the true meaning of
Japanese phrase,“his/her character just like splitting a bamboo竹を割ったような性格.”Dividing a bamboo log
is really “with a good grace.”

We
made lots of bamboo sticks ...

and
stuffed them in the drum ...

tightly.

The
pipes welded at the bottom wall of a drum have important function. To make
complete combustion of incomplete combustion, we have to let the volatile
substance inside the bamboo free to evaporate. The pipes are for these gasses
to escape from the drum. Before stuffing the drum with bamboos my senior Lovers
cleaned the pipes carefully to remove clogs. After filling the drum, a lid is
put on it and sealed with the red clay mud to establish the flow of heat one-way,
from the gutter to 4 pipes, as much as possible. After 17 years of operation,
the supply of red clay becoming somehow smaller, the seniors say. Red clay is typical soil in Kanto region especially where the volcanic ashes from Mt Fuji fell when
it erupted. I asked if we can just dig up the land wherever allowed in the Niiharu
Forest to replenish the stock. “Huh? Of course not. Niiharu is rich forest with
lots of fallen leaves and the other organic materials. When we use the soil
from here directly, those organic materials will be burned during the charcoal cooking,
and the mud cannot seal the kilns tightly.” Oh, I see.

Cleaning
the pipes …

and
drums.When we opened the lid at the beginning of the season,inside of a drum
was a home of a cricket.Cute. 😄

Making
red clay mud for sealing.

Shutting
the lid tightly, and

Sealing
it with clay mud.The stick over the lid is a pipe for inserting a thermostatduring the operation.

We
pile up the mud over the lid further …

until
the kiln looks like this.

The
volatile compounds vaporized during charcoal making are that problematic smoke
the Hikarigaoka Housing Complex complained to the volunteers of Shikinomori
Park. It is that much. It cannot be dealt with the tiny 4 pipes poking out from
a drum. In addition, when the vapor cools it becomes useful wood vinegar so
that we want to catch it while its cooling. The Lovers mount extensions of the
pipes. Here is another clever way Niiharu employs for charcoal cooking. We went
into bamboo forest and harvested 3 to 5 years old large bamboo logs with 15cm
or so diameter. With a long metal pole, my seniors punched the wall of each
node that separated sections inside of the harvested bamboo logs. Voilà! Long bamboo trunks turned into long
chimney pipes. According to the seniors, a bamboo chimney works well for about
2 seasons. When it’s time to replace, we simply return them to the forest, and
they go into mulch over the ground. Meanwhile, the supply of new boles is not
the issue thanks to vigorous bamboos. Sustainable, isn’t it?

New
chimney pipes

The
end of each bamboo pipesare cut like these …

And
set up at the pipes coming fromthe bottom of the drum like this.

A
shorter log of a bamboo acts like a bucket.When the fume comes out from the
drum,it cools down rapidly by winter air, and liquefies.It’s original
solution of wood vinegarthat is to be collected with this bamboo bucket.

The
bamboo pipes extend out of the hut.

Now,
we are ready to start cooking! I tell you my whole day adventure of charcoal
making next week. 😊

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About Me

My
family moved to Yokohama from Tokyo before I became 3 years old. Since then,
Yokohama is my home town. (Though, I cannot be Hamakko since I was born in Tokyo ... Hey, this is Japan!) I have watched my playground is changing always. I
hope you find Yokohama interesting place. With love, Naomi